Acoustic backing with integral conductors for an ultrasonic transducer

Abstract

A two phase composite acoustic backing for an ultrasonic transducer array is formed of a first composite material which is electrically conductive and relatively attenuative to acoustic energy and forms a plurality of isolated conductive paths between individual elements of the array and the back side of said backing. The isolated conductive paths are surrounded by an acoustic kerf filler material which is non-conductive and is either attenuative to acoustic energy, exhibits a low acoustic impedance, or both. The resulting two phase composite acoustic backing thus attenuates ultrasonic energy which enters the backing from the transducer elements, both in the conductive paths and in the surrounding kerf filler material, while affording points of electrical attachment to cable wires for the array which are removed from the piezoelectric material.

What is claimed is: 
     
       1. A composite acoustic backing for an ultrasonic transducer array of piezoelectric elements, comprising: regions of a first composite material which is electrically conductive and relatively attenuative to acoustic energy, said regions being relatively acoustically and electrically isolated from each other and acoustically and electrically coupled to individual elements of the array to provide electrical paths between said elements and an external surface of said backing; and   regions of a second material which is electrically non-conductive and attenuative to acoustic energy, said regions of second material providing acoustic and electrical isolation between said regions of said first composite material.   
     
     
       2. The composite acoustic backing of claim 1, further comprising separate signal connecting electrodes located in registration with terminating surfaces of said regions of said first composite material, wherein said regions of said first composite material are electrically connected to said signal connecting electrodes. 
     
     
       3. The composite acoustic backing of claim 1, wherein said first material comprises a polymeric material loaded with metallic particles, and wherein said second material comprises an acoustic kerf filler material. 
     
     
       4. The composite acoustic backing of claim 3, wherein said metallic particles comprise tungsten or silver particles, and wherein said acoustic kerf filler material comprises an epoxy, a polyurethane, or a silicone rubber compound. 
     
     
       5. The composite acoustic backing of claim 1, wherein said ultrasonic transducer array extends in either one or two dimensions. 
     
     
       6. A composite acoustic backing for an ultrasonic transducer array of piezoelectric elements, comprising: regions of a first composite material which is electrically conductive, relatively attenuative to acoustic energy, and exhibits a given acoustic impedance, said regions being relatively acoustically and electrically isolated from each other and acoustically and electrically coupled to individual elements of the array to provide electrical paths between said elements and an external surface of said backing; and   regions of a second material which is electrically non-conductive and exhibits a low acoustic impedance relative to that of said first composite material, said regions of second material providing acoustic and electrical isolation between said regions of said first composite material.   
     
     
       7. The composite acoustic backing of claim 6, further comprising separate signal connecting electrodes located in registration with terminating surfaces of said regions of said first composite material, wherein said regions of said first composite material are electrically connected to said signal connecting electrodes. 
     
     
       8. The composite acoustic backing of claim 6, wherein said first material comprises a polymeric material loaded with metallic particles, and wherein said second material comprises an acoustic kerf filler material. 
     
     
       9. The composite acoustic backing of claim 8, wherein said metallic particles comprise tungsten or silver particles, and wherein said acoustic kerf filler material comprises a blend of epoxy and micro balloons. 
     
     
       10. The composite acoustic backing of claim 6, wherein said ultrasonic transducer array extends in either one or two dimensions. 
     
     
       11. A composite acoustic backing for an ultrasonic transducer array of piezoelectric elements having a transducer contacting first surface and a signal connecting second surface opposite said first surface comprising: regions of a first material which is relatively poorly electrically conductive and relatively attenuative to acoustic energy, said regions being relatively acoustically and electrically isolated from each other and extending substantially between said first and second surfaces, each of said regions having an external layer of a relatively highly electrically conductive material extending substantially between said first and second surfaces, said regions being spatially in registration with and acoustically coupled to individual elements of the array such that said layers of conductive material provide electrical paths between said elements and said signal connecting second surface of said backing; and   regions of a second, kerf filler material which is electrically non-conductive and attenuative to acoustic energy, said regions of second material providing acoustic and electrical isolation between said layers of conductive material.   
     
     
       12. The composite acoustic backing of claim 11, further comprising separate signal connecting electrodes located on said signal connecting second surface of said backing, wherein said layers of conductive material are electrically connected to said signal connecting electrodes. 
     
     
       13. The composite acoustic backing of claim 11, further comprising a plurality of separate electrodes located on said transducer contacting first surface in registration with said individual elements of said array and electrically connected to said layers of conductive material for making electrical connection between said layers of conductive material and said elements of said array. 
     
     
       14. A composite acoustic backing for an ultrasonic transducer array of piezoelectric elements having a transducer contacting first surface and a signal connecting second surface opposite said first surface comprising: conductors including central regions of a first material which is electrically non-conductive, relatively attenuative to acoustic energy, and exhibits a given acoustic impedance, said regions being relatively acoustically and electrically isolated from each other and extending substantially between said first and second surfaces, each of said regions having an outer layer of conductive material extending substantially between said first and second surfaces, said conductors being spatially in registration with and acoustically coupled to individual elements of the array such that said layers of conductive material provide electrical paths between said elements and said signal connecting second surface of said backing; and   regions of a second material which is electrically non-conductive and exhibits a low acoustic impedance relative to that of said first material, said regions of second material providing acoustic and electrical isolation between said conductors.   
     
     
       15. The composite acoustic backing of claim 14, further comprising separate signal connecting electrodes located on said signal connecting second surface of said backing, wherein said layers of conductive material are electrically connected to said signal connecting electrodes. 
     
     
       16. The composite acoustic backing of claim 14, further comprising a plurality of separate electrodes located on said transducer contacting first surface in registration with said individual elements of said array and electrically connected to said layers of conductive material for making electrical connection between said layers of conductive material and said elements of said array.